Communications devices, such as two way radios and cellular phones, are frequently used in noisy environments which can make listening to received speech audio problematic. In a full duplex communications system such as a cellphone system, bidirectional communication is continuous. Noise samples are easily obtainable at both ends of the communications channel since both sides are simultaneously active, usually for long periods of time (e.g. minutes). Thus, noise adaptive signal processing methods designed to improve speech quality in noise in full duplex systems usually have more than sufficient time to sample background noise and adapt output speech for the listener to ambient noise conditions. In addition, since cellphones are normally held at the ear, a limited amount of audio gain increase (i.e. loudness) is usually sufficient to overcome the effects of high ambient noise. This gain increase modification usually can be performed in software by simply scaling the signal amplitude within the limits of its numerical representation prior to the device output audio amplifier.
Half-duplex speech communication devices, such as two-way radios, are widely used by enterprises and governments. In a half-duplex system, either the transmit (e.g., a transmit state) or receive side (e.g., a receive state) is active at one time. When not active (i.e. not receiving or transmitting a signal) the radio is usually placed in a reduced power idle state (i.e. sleep mode to conserve power) until an incoming signal is received or the transmit state is activated. When a downlink signal/message is received the radio needs to “wake up” to process the incoming signal. This wakeup period is often short (tens or hundreds of milliseconds). In addition, half-duplex transmitted messages, such as those common in public safety use environments, tend to be much shorter than messages conveyed in a full-duplex public cellphone communications environment so the time available to estimate the noise and complete noise adaptation to enhance the message audio also tends to be very short. These time limiting half-duplex radio operating conditions make noise estimation and noise-adaptive signal conditioning more problematic than for full-duplex systems. Also, two-way half-duplex radios are frequently used by public safety and commercial users in variable, rapidly changing, extreme noise environments (e.g. airports, factories, fire scenes, stadiums, etc.) and are typically held away from the ear (e.g. forearm, shoulder, belt, console position). This requires a higher audio volume output to overcome the ambient noise.
Accordingly, there is a need for an improved method and apparatus for adapting volume control for half-duplex communication devices.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.